Wheel assembly and robot cleaner having same

ABSTRACT

Disclosed herein are a wheel assembly and a robot cleaner including a main body and a wheel assembly coupled to the main body to guide movement of the main body. The wheel assembly has a rotation arm including a first end portion rotatably mounted on the main body, a drive wheel rotatably installed on a second end portion of the rotation arm opposite the first end portion, and an elastic member including a first end installed at the main body and a second end vertically moveably installed at the rotation arm opposite the first end, such that a reduction degree of a contact force due to a descent of the drive wheel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of U.S. application Ser.No. 15/767,255, filed Apr. 10, 2018 which is a National PhaseApplication under U.S.C. § 371 of PCT International Patent ApplicationNo. PCT/KR2016/013214, filed Nov. 16, 2016 which claims the foreignpriority benefit under 35 U.S.C. § 119 to Korean Patent Application No.10-2015-0163196 filed Nov. 20, 2015, the contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a wheel assembly and a robot cleanerhaving the same, and more particularly, to a structural improvement fora contact force of a drive wheel.

BACKGROUND ART

Generally, robot cleaners are devices configured to automatically travelin a region to be cleaned according to a preset program to suctionforeign materials such as dust from a ground surface and to clean theregion without a user's manipulation.

Such a robot cleaner includes a drive wheel for driving a main body of arobot cleaner, and the drive wheel drives the main body of the robotcleaner using a frictional force generated between the drive wheel and aground surface in contact with the drive wheel.

A force applied to the drive wheel toward the ground surface is neededto generate the frictional force, and the force relates to a contactforce of the robot cleaner.

A robot cleaner has to maintain a predetermined contact force of a drivewheel regardless of a state or condition of a ground surface to havepredetermined traveling performance on a floor such as a hard floor orcarpet having differences in various floor conditions and heights.

Conventionally, although an elastic member, such as a tension coilspring, is used to press a drive wheel against a ground surface, sincean elastic force of the elastic member is changed according to adisplacement of the drive wheel when a robot cleaner is used on a groundsurface having a height difference, a difference in magnitude of a forcepressing the drive wheel occurs, and accordingly, there is a problem inthat a contact force of the drive wheel is decreased.

DISCLOSURE Technical Problem

The present disclosure is directed to a wheel assembly improved todecrease a change in a contact force of a drive wheel even in a case inwhich there is a change in a displacement of the drive wheel when arobot cleaner travels on a ground surface having a height difference,and a robot cleaner having the same.

Technical Solution

In accordance with one aspect of the present disclosure to provide arobot cleaner including a main body, and a wheel assembly coupled to themain body and configured to guide movement of the main body, wherein thewheel assembly includes a rotation arm including a first end portionrotatably installed in the main body; a drive wheel rotatably installedat a second end portion of the rotation arm opposite the first endportion, and an elastic member including a first end installed at themain body and a second end vertically moveably installed at the rotationarm opposite the first end.

The rotation arm may include a guide configured to vertically extendfrom the first end portion and the second end of the elastic member ismoveably installed at the guide.

The guide may include a guide portion configured to guide movement ofthe first end of the elastic member, and a pair of stoppers provided atupper and lower ends of the guide portion and configured to restrictmovement of the second end of the elastic member.

The elastic member may include an elastic portion formed in a coil form,a first hook supported by the main body, and a second hook supported bythe guide portion.

The robot cleaner may further include a moving bush formed in an arcshape and moveably installed at the guide portion, wherein the movingbush includes a seating groove which is provided in a circumferentialdirection and in which the second hook is seated.

The robot cleaner may further include a roller moveably installed on theguide portion, wherein the second hook is connected to the roller.

The robot cleaner may further include a bearing installed at a center ofthe roller, and a holder including both ends coupled to the bearing by ashaft, wherein the first hook is supported by the holder.

The guide portion may be formed in a linear shape.

The guide portion may include two line sections obliquely connected toform an obtuse angle.

The guide portion may be formed in a concavely curved shape.

The robot cleaner may further include a pinion moveably installed on theguide portion formed as a rack gear, and a holder having both endscoupled to the pinion by a shaft, wherein the second hook is supportedby the holder.

The guide portion may be formed in an inner gear form.

The wheel assembly may be provided with a pair of wheel assembliescoupled to both sides of the main body.

In accordance with an another aspect of the present disclosure toprovide a wheel assembly including a wheel housing, a drive wheeldisposed movably downwardly in the wheel housing, a rotation armrotatable about a first end portion thereof and having a second endportion opposite to the first end portion on which the drive wheel, andan elastic member having a first end provided on the wheel housing and asecond end provided on the opposite side of the first end to bevertically movable on the rotation arm.

In accordance with an another aspect of the present disclosure toprovide a method of operating a wheel assembly including a rotation armhaving a first end portion rotatably installed at a moving object, adrive wheel rotatably installed at a second end portion of the rotationarm opposite the first end portion, and an elastic member having a firstend installed at the object and a second end disposed opposite the firstend and vertically moveably installed at the rotation arm, the methodincluding rotating the rotation arm about the first end portion, movingthe drive wheel disposed at the second end portion of the rotation armdownward, and moving the second end of the elastic member upwardaccording to the downward movement of the drive wheel.

A guide configured to guide the movement of the second end of theelastic member is provided at the first end portion of the rotation arm,and an angle between the elastic member and the guide is graduallychanged from an obtuse angle to an acute angle according to the downwardmovement of the drive wheel.

Advantageous Effects

As described above, in a wheel assembly and a robot cleaner having thesame, since a drive wheel is moved downward according to rotation of arotation arm, a position of a second end of an elastic member is awayfrom a rotation center of the rotation arm, a torque applied to therotation arm is increased such that a reduction degree of a contactforce of the drive wheel due to a reduction of an elastic restoringforce of the elastic member is decreased.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view illustrating a robot cleaner according to afirst embodiment of the present disclosure.

FIG. 2 is a view illustrating the robot cleaner according to the firstembodiment of the present disclosure when the robot cleaner passesthrough a flat surface.

FIG. 3 is a view illustrating the robot cleaner according to the firstembodiment of the present disclosure when the robot cleaner passesthrough a floor having a height difference.

FIG. 4 is a perspective view illustrating an installation state of awheel assembly in a robot cleaner according to the first embodiment ofthe present disclosure.

FIG. 5 is a perspective view illustrating the wheel assembly accordingto the first embodiment of the present disclosure.

FIG. 6 is an exploded perspective view illustrating the wheel assemblyaccording to a first embodiment of the present disclosure.

FIG. 7 is an exploded perspective view illustrating an installationstate of a moving bush applied to the wheel assembly according to thefirst embodiment of the present disclosure.

FIG. 8 is a side view illustrating the wheel assembly according to thefirst embodiment of the present disclosure.

FIGS. 9 to 11 are operational states of the wheel assembly according tothe first embodiment of the present disclosure.

FIG. 12 is a perspective view illustrating an installation state of aroller and a holder applied to a wheel assembly according to a secondembodiment of the present disclosure.

FIG. 13 is a side view illustrating the wheel assembly according to thesecond embodiment of the present disclosure.

FIGS. 14 to 16 are side views illustrating various other types of guidesapplied to a wheel assembly according to the present disclosure.

FIG. 17 is a perspective view illustrating the installation state of apinion and a holder applied to a wheel assembly according to a thirdembodiment of the present disclosure.

FIG. 18 is a side view illustrating the wheel assembly according to thethird embodiment of the present disclosure.

FIG. 19 is a side view illustrating another type of guide that can beapplied to the third embodiment of the present disclosure.

FIG. 20 is a graph illustrating normal force on a drive wheel accordingto embodiments of the present disclosure.

MODES OF THE DISCLOSURE

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings.

FIG. 1 is a view illustrating a robot cleaner 1 according to a firstembodiment of the present disclosure.

The robot cleaner 1 includes a main body 10 forming an exterior thereof,a suction unit 20 coupled to one side of the main body 10 and configuredto suction air around a floor, and wheel assemblies 30 disposed at bothsides of the main body 10 as illustrated in FIG. 4 and configured toallow the main body 10 to move on a ground surface.

Referring back to FIG. 1, the main body 10 includes a fan motor 11configured to generate a suction force and a dust collecting container12 configured to store foreign materials such as dust filtered from airsuctioned through the suction unit 20.

The suction unit 20 suctions foreign materials of a ground surface withair using a suction force transmitted from the fan motor 11. Althoughnot illustrated in the drawings, a brush is rotatably installed in thesuction unit 20 to swipe dust on the ground surface upward.

In a case in which the robot cleaner 1 moves along a flat surface, thewheel assembly 30 maintains a state in which the main body 10 isadjacent to the ground surface, as illustrated in FIG. 2, and in a casein which the robot cleaner passes a place having a height differencesuch as a threshold, the wheel assembly 30 allows the main body 10 to bespaced apart from the ground surface, as illustrated I FIG. 3.

As illustrated in FIGS. 5 and 6, the wheel assembly 30 includes arotation arm 31 having a first end portion 31 a provided at one sidethereof and rotatably installed in the main body 10, a drive wheel 32installed at a second end portion 31 b of the rotation arm 31 oppositethe first end portion 31 a, a drive motor 33 coupled to a side of thefirst end portion of the rotation arm 31 and configured to generate arotational force for rotating the drive wheel 32, an elastic member 34configured to elastically support the rotation arm 31 to maintain apredetermined contact force or more between the drive wheel 32 and aground surface, and a wheel housing 35 configured to accommodate thedrive wheel 32.

Since the first end portion 31 a of the rotation arm 31 is rotatablyinstalled at the main body 10 as described above, the second end portion31 b of the rotation arm 31 moves downward as the rotation arm 31rotates about the first end portion 31 a.

A motor installation portion 311 in which the drive motor 33 isinstalled is provided at the first end portion 31 a of the rotation arm31, and a wheel installation portion 312 in which the drive wheel 32 isinstalled is provided at the second end portion 31 b of the rotation arm31. In addition, a power transmission unit such as a belt or gear fortransmitting the rotational force generated by the drive motor 33 to thedrive wheel 32, is installed inside the rotation arm 31. Accordingly, asthe second end portion 31 b of the rotation arm 31 moves downward, thedrive wheel 32 is moved downward.

The elastic member 34 is formed of a coil spring, a first end 34 b ofthe elastic member 34 is hooked on and supported by a support 35 cprovided at the wheel housing 35, and a second end 34 c of the elasticmember 34 is supported by a guide 313 of the rotation arm 31.Accordingly, in a case in which a weight of the robot cleaner 1 appliedto the drive wheel 32 decreases, the second end portion 31 b of therotation arm 31 and the drive wheel 32 installed at the second endportion 31 b of the rotation arm 31 are moved downward due to an elasticrestoring force of the elastic member 34.

The elastic member 34 includes an elastic portion 34 a formed in a coilform and configured to generate the elastic force, a first hook 34 bforming the first end 34 b of the elastic member 34 and supported by thesupport 35 c, and a second hook 34 c forming the second end 34 c of theelastic member 34 and supported by the guide 313 of the rotation arm 31.That is, the first hook 34 b is the first end 34 b of the elastic member34 and the second hook 34 c is the second end 34 c of the elastic member34.

The wheel housing 35 includes an arm accommodation portion 35 a in whichthe rotation arm 31 is rotatably accommodated and a wheel accommodationportion 35 b in which the drive wheel 32 is rotatably accommodated. Inaddition, the above-described support 35 c is provided in the wheelhousing 35.

Accordingly, while the robot cleaner 1 moves on a flat surface, a statein which the drive wheel 32 is accommodated in the wheel accommodationportion 35 b due to the weight of the robot cleaner 1 is maintained, andwhen the robot cleaner 1 passes a place such as a threshold, since theweight of the robot cleaner 1 transmitted to the drive wheel 32decreases, the rotation arm 31 rotates about the first end portion 31 awhile the elastic member 34 is elastically restored, and accordingly,the second end portion 31 b of the rotation arm 31 and the drive wheel32 installed at the second end portion 31 b are moved downward.

As described above, since the elastic member 34 is gradually elasticallyrestored as the drive wheel 32 moves downward, the contact force of thedrive wheel 32 maintained due to the elastic restoring force of theelastic member 34 gradually decreases as the drive wheel 32 movesdownward.

Since the second end 34 c of the elastic member 34 is installed at therotation arm 31 to be moveable upward and downward to decrease theamount of reduction of the contact force due to the descent of the drivewheel 32, the second end 34 c of the elastic member 34 is moved upwardaccording to the descent of the drive wheel 32.

The rotation arm 31 includes the guide 313 extending upward from theside of the first end portion 31 a and configured to guide movement ofthe second end of the elastic member 34.

The guide 313 includes a guide portion 313 a at which the second end ofthe elastic member 34 is vertically moveably installed and a pair ofstoppers 313 b and 313 c provided at upper and lower ends of the guideportion 313 a and configured to allow the second end of the elasticmember 34 to move in the guide portion 313 a. In the present disclosure,the guide portion 313 a is substantially formed in a linear shape. Here,the guide portion 313 a is designed such that an obtuse angle betweenthe guide portion 313 a and the elastic member 34 s is maintained in astate in which the drive wheel 32 is accommodated in the wheelaccommodation portion 35 b, and an acute angle is formed between theguide portion 313 a and the elastic member 34 when the drive wheel 32protrudes from the wheel accommodation portion 35 b by a predetermineddegree or more as the rotation arm 31 gradually rotates.

Since the second hook 34 c of the elastic member 34 is moveablyinstalled at the above-described guide portion, the second hook 34 c issupported by the guide portion 313 a using a moving bush 36 asillustrated in FIG. 7 such that the second hook 34 c is easily moved.The moving bush 36 is formed in a substantially arc shape, and a seatinggroove 36 a on which the second hook 34 c seats is provided in an outercircumferential surface of the moving bush 36.

Next, operations of the wheel assembly and the robot cleaner will bedescribed in detail with reference to the accompanying drawings.

As illustrated in FIGS. 8 and 9, in a case in which the robot cleaner 1cleans a flat surface, since the weight of the robot cleaner 1 isdirectly transmitted to the drive wheel, a state in which the drivewheel 32 is accommodated in the wheel accommodation portion 35 b of thewheel housing 35 is maintained without change.

In the above state, when the robot cleaner 1 passes a place such as athreshold having a height difference, the weight of the robot cleaner 1transmitted to the drive wheel 32 decreases, and accordingly, therotation arm 31 rotates about the first end portion 31 a due to theelastic restoring force of the elastic member 34. The drive wheel 32installed at the second end portion 31 b of the rotation arm 31 is moveddownward according to rotation of the rotation arm 31 and graduallyprotrudes downward from the wheel accommodation portion 35 b.

As described above, the guide 313 provided at the first end portion 31 aof the rotation arm 31 is also rotated together with the rotation arm 31according to the rotation of the rotation arm 31. As the rotation arm 31is rotated, an angle θ between the guide portion 313 a provided at theguide 313 and the elastic member 34 is changed from an obtuse angle, asillustrated in FIG. 9, to a right angle, as illustrated in FIG. 10, andis finally changed to an acute angle, as illustrated in FIG. 11, due toa restoring force of the elastic member 34. When the angle between guideportion 313 a and the elastic member 34 is the acute angle, as describedabove, the moving bush 36 accordingly slides along a surface of theguide portion 313 a and is moved upward to a position at which a rightangle between the moving bush 36 and the guide 313 is maintainable. Inaddition, when the rotation arm 31 is continuously rotated, the movingbush 36 is continuously moved upward until the moving bush 36 is stoppeddue to the stopper 313 b. When the rotation arm 31 is continuouslyrotated even after the moving bush 36 is supported by the upper stopper313 b, the angle between the guide portion 313 a and the elastic member34 is an acute angle, and such an angle decreases according to therotation of the rotation arm 31.

When the second end 34 c of the elastic member 34 is moved upward, sincea position of the second end 34 c elastically supported by the elasticmember 34 is far from a rotation center of the rotation arm 31, a torqueapplied to the rotation arm 31 by the elastic member 34 is greater thanthat of a case in which the second end of the elastic member 34 islocated below the guide portion 313 a, and thus a contact force of thedrive wheel 32 is increased. Accordingly, a reduction degree of thecontact force of the drive wheel 32 according to the rotation of therotation arm 31 is decreased by changing the position of the second endof the elastic member 34.

FIG. 20 is a graph showing a normal force applied to the drive wheel 32when the second end 34 c is moved below the drive wheel 32. In thedrawing, line A shows a normal force applied to the drive wheel 32 in acase in which the second end is moved below the drive wheel 32 in astate in which the second end of the elastic member 34 is fixed like aconventional technology, and line B shows a normal force applied to thedrive wheel 32 in a case in which the second of the elastic member 34 ismoved like the first embodiment of the present disclosure. Since thecontact force of the drive wheel 32 is proportional to the normal force,a reduction degree of the contact force may be decreased by the secondend of the elastic member 34 being moved as illustrated in the drawing.

Hereinafter, a wheel assembly according to a second embodiment of thepresent disclosure will be described in detail with reference to theaccompanying drawings.

As illustrated in FIGS. 12 and 13, a wheel assembly 30 according to thesecond embodiment of the present disclosure includes a drive wheel 32, arotation arm 31, an elastic member 34, and a wheel housing 35 which havethe same forms as those of the previous embodiment.

In addition, a second end of the elastic member 34 is moveably supportedby a guide portion 313 a through a roller 371 moveably installed at theguide portion 313 a, a bearing 372 installed at a center of the roller371, and a holder 374 formed in a U shape and having both ends coupledto a bearing 372 via a shaft 373. The second hook 34 c of the elasticmember 34 is supported by being hooked at a center of the holder 374.Due to the above configuration, the second end of the elastic member 34may be more easily moved along the guide portion 313 a.

The guide portion 313 a is formed in a linear shape in theabove-described embodiments, but is not limited thereto. As illustratedin FIG. 14, a guide 313-1 may include a guide portion 313 a-1 having twolines obliquely connected to form an obtuse angle, or, as illustrated inFIG. 15, a guide 313-2 may also include a guide portion 313 a-2 formedin a concavely curved shape. In addition, as illustrated in FIG. 16, aguide 313-3 may also include a guide portion 313 a-3 having a lowerportion formed in a concavely curved shape and an upper portion having aconvexly curved shape.

Hereinafter, a wheel assembly 30 according to a third embodiment of thepresent disclosure will be described in detail with reference to theaccompanying drawings.

As illustrated in FIGS. 17 and 18, the wheel assembly according to thethird embodiment of the present disclosure includes a drive wheel 32, arotation arm 31, an elastic member 34, and a wheel housing which havethe same forms as those of the previous embodiment, and a guide 313-4includes a guide portion 313 a-4 formed in a rack gear form.

In addition, a second end of the elastic member 34 is moveably installedat a guide portion 313 a through a pinion 381 tooth-engaged with theguide portion 313 a-4 formed in the rack gear form and a holder 383formed in a U shape and having both ends rotatably coupled to the pinion381 by a shaft 382. A second hook 34 c of the elastic member 34 issupported by being hooked at a center of the holder 383. Due to theabove configuration, the second end of the elastic member 34 may be moreeasily moved along the guide portion 313 a-4.

Line C of FIG. 20 shows a normal force of the drive wheel 32 accordingto a structure in which the second end of the elastic member 34 may bemoved by the guide portion 313 a formed in the rack gear form and thepinion 381.

In the embodiment, the guide portion 313 a includes a rack gear in alinear shape, but is not limited thereto, and, as illustrated in FIG.19, a guide 313-5 may also include a guide portion 313 a-5 formed in aninner rack gear form.

Although the second end of the elastic member having the structure inwhich the second end is vertically moveably installed in theabove-described embodiments, the embodiments are not limited thereto,and a first end of an elastic member installed at a side of a main bodymay also be moveable upward and downward.

In addition, in the above-described embodiments, the wheel assembly isinstalled in the robot cleaner 1 and the robot cleaner 1 moves, but theembodiments are not limited thereto, and the wheel assembly may also beapplied to various moving objects other than the robot cleaner. That is,the wheel assembly may also be applied to various different kinds ofmoving robots, vehicles, and the like other than the robot cleaner.

Although the spirit of the present disclosure has been disclosed on thebasis of the various embodiments as described above, the scope of thepresent disclosure is not limited to the embodiments. Various otherembodiments that may be changed or modified by those skilled in the artwithout departing from the scope and spirit of the present disclosuredefined by the appended claims fall within the scope of the presentdisclosure.

1. A robot cleaner comprising: a main body; and a wheel assembly coupledto the main body and configured to guide movement of the main body;wherein the wheel assembly includes: a drive wheel; a rotation armincluding a first rotation shaft rotatably coupled to the main body, asecond rotation shaft to which the drive wheel is rotatably coupled, anda guide formed to extend from the rotation arm; and an elastic memberincluding a first end coupled to the main body and a second end oppositeto the first end, the second end coupled to the guide and configured toslide on the guide so as to be moveable along the guide.
 2. The robotcleaner of claim 1, wherein the guide is configured to vertically extendfrom the first rotation shaft.
 3. The robot cleaner of claim 2, whereinthe guide includes: a guide portion configured to guide movement of thesecond end of the elastic member; and a pair of stoppers provided atupper and lower ends of the guide portion and configured to restrictvertical movement of the second end of the elastic member.
 4. The robotcleaner of claim 3, wherein the elastic member includes: an elasticportion formed in a coil form; a first hook supported by the main body;and a second hook supported by the guide portion.
 5. The robot cleanerof claim 4, further comprising a moving bush formed in an arc shape andmoveably installed at the guide portion, wherein the moving bushincludes a seating groove which is provided in a circumferentialdirection and in which the second hook is seated.
 6. The robot cleanerof claim 4, further comprising a roller moveably installed on the guideportion, wherein the second hook is connected to the roller.
 7. Therobot cleaner of claim 6, further comprising: a bearing installed at acenter of the roller; and a holder including both ends of the holdercoupled to the bearing by a shaft, wherein the second hook is supportedby the holder.
 8. The robot cleaner of claim 3, wherein the guideportion is formed in a linear shape.
 9. The robot cleaner of claim 3,wherein the guide portion includes two line sections obliquely connectedto form an obtuse angle.
 10. The robot cleaner of claim 3, wherein theguide portion is formed in a concavely curved shape.
 11. The robotcleaner of claim 5, further comprising: a pinion moveably installed onthe guide portion formed as a rack gear; and a holder having both endscoupled to the pinion by a shaft, wherein the second hook is supportedby the holder.
 12. The robot cleaner of claim 11, wherein the guideportion is formed in an inner gear form.
 13. The robot cleaner of claim1, wherein the wheel assembly is provided with a pair of wheelassemblies coupled to both sides of the main body.
 14. A method ofoperating a wheel assembly including a rotation arm having a firstrotation shaft rotatably coupled to a moving object and having a guideextending from the rotation arm, a drive wheel rotatably coupled to asecond rotation shaft of the rotation arm opposite the first rotationshaft, and an elastic member having a first end coupled to the movingobject and having a second end disposed opposite the first end andconfigured to slide on the guide so as to be moveable with respect tothe rotation arm, the method comprising: rotating the rotation arm aboutthe first rotation shaft; moving the drive wheel disposed at the secondrotation shaft of the rotation arm downward; and sliding the second endof the elastic member upward on the guide based on a downward movementof the drive wheel.
 15. The method of claim 14, wherein: the guide isconfigured to guide the movement of the second end of the elasticmember; and an angle between the elastic member and the guide isgradually changed from an obtuse angle to an acute angle according tothe downward movement of the drive wheel.